BUG#14480, attempt2: In CREATE ... SELECT ..., don't count the same field twice

when calculating table->null_fields.


mysql-test/r/create.result:
  Testcase for BUG#14480
mysql-test/t/create.test:
  Testcase for BUG#14480
sql/sql_table.cc:
  BUG#14480: For CREATE ... SELECT ... a field list passed to mysql_prepare_table() contains
  instances of create_field for both create-list and select-list. mysql_prepare_table() 
  matches elements that refer to the same field, and joins them together. When the "join"  
  is performed, both of create_field structures has already been counted in "null_fields". 
  
  This fix makes sure that "null_fields" contains the correct value after two create_field 
  structures have been joined.

1 files changed, 8 insertions, 1 deletions

diff --git a/sql/sql_table.cc b/sql/sql_table.cc
index dcbc2018b49..40777682251 100644
--- a/sql/sql_table.cc
+++ b/sql/sql_table.cc
@@ -647,8 +647,15 @@ int mysql_prepare_table(THD *thd, HA_CREATE_INFO *create_info,
           sql_field->pack_length=	dup_field->pack_length;
 	  sql_field->create_length_to_internal_length();
 	  sql_field->decimals=		dup_field->decimals;
-	  sql_field->flags=		dup_field->flags;
 	  sql_field->unireg_check=	dup_field->unireg_check;
+          /* 
+            We're making one field from two, the result field will have
+            dup_field->flags as flags. If we've incremented null_fields
+            because of sql_field->flags, decrement it back.
+          */
+          if (!(sql_field->flags & NOT_NULL_FLAG))
+            null_fields--;
+	  sql_field->flags=		dup_field->flags;
 	  it2.remove();			// Remove first (create) definition
 	  select_field_pos--;
 	  break;